DRV8461SPWPR datasheet(40/117 Pages) TI

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is oberved around the zero crossing, the value of sampling time can be increased to a maximum of 5 μs. The

following scopeshot shows an example of transition from silent step decay mode to smart tune ripple control

decay mode with a sampling time of 5 μs.

Traces from top to bottom: AOUT2, AOUT1, coil A current, coil B current, nSCS

Figure 7-20. Silent step to smart tune transition

7.3.12 Auto-torque Dynamic Current Adjustment

For a typical stepper motor driver, the full-scale current is designed based on the peak load torque demand. This

ensures that the motor does not lose steps any time peak load is demanded. The current therefore is constant

irrespective of the load torque. As a result, when load torque is lower than the peak load, the driver and the

motor dissipate some of the input power as resistive power loss as represented in Figure 7-21.

Margin

Maximum Torque

Power Loss

Op mal Current

Output Current

Time

Figure 7-21. Power Loss with Conventional Stepper Driver

In most systems, the demand for peak load torque occurs only rarely. For example, in an ATM machine, the

stepper motors might be needed to deliver peak load for less than 15% of their overall run time. A typical stepper

driver though ends up delivering full-scale current to the motors all the time - leading to lower system efficiency

due to the unwanted power loss, larger system size and shorter lifetime of components.

DRV8461

SLOSE98 – DECEMBER 2022

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DRV8461SPWPR Datasheet(PDF) 40 Page - Texas Instruments